Glutathione‐protein mixed disulfide decreases the affinity of rat liver fatty acid‐binding protein for unsaturated fatty acid

Abstract

0.16 ± 0.062% of the fatty acid‐binding protein purified from 50 mM N‐ethylmaleimide‐treated rat liver (L‐FABP) was determined as a form S‐thiolated by glutathione (L‐FABP‐SSG). L‐FABP‐SSG, which was prepared in vitro through thiol – disulfide exchange reaction, showed more acidic pI (∼ 5.0) than the pI (∼ 7.0) of reduced L‐FABP. S‐thiolation of L‐FABP by glutathione decreased the affinity of the protein for unsaturated fatty acids without changing the equimolar maximum binding. The changes in Kd were from 0.63 ± 0.054 μM to 1.03 ± 0.14 μM for oleic acid, from 0.63 ± 0.028 μM to 0.97 ± 0.12 μM for linoleic acid and from 0.85 ± 0.050 μM to 1.45 ± 0.024 μM for arachidonic acid. This modification did not alter the affinity nor the maximum binding for saturated fatty acids, which were determined to be Kd of ∼ 1.0 μM for palmitic acid and ∼ 0.9 μM for stearic acids, and equimolar maximum binding for both fatty acids. The binding affinity of L‐FABP for unsaturated fatty acid may be regulated by redox state of the liver. Copyright © 1990, Wiley Blackwell. All rights reserved